Headbox for papermaking machine



06L 1969 N. M. REITZEL HEADBOX FOR PAPERMAKING MACHINE Filed Feb. 24, 1966 INVENTOR NICOLAS M. REITZEL BY f ATTORNEY United States Patent 3,471,368 HEADBOX FOR PAPERMAKING MACHINE Nicolas M. Reitzel, Kendall Place, Boylston, Mass. 01505 Filed Feb. 24, 1966, Ser. No. 529,716 Int. Cl. D21f 1/06, 1/00 US. Cl. 162--338 4 Claims ABSTRACT OF THE DISCLOSURE A headbox for papermaking machinery including a distribution chamber and a subsequent chamber for the stock to be deposited on a wire, passages between the chambers for high velocity discharge of stock into the subsequent chamber from the distribution chamber, a headbox chamber and a screen between the subsequent chamber and the headbox chamber through which the stock must pass where in the energy of the high velocity stock is dissipated as increased turbulence in the stream at the upside of the screen.

In a papermaking machine, a headbox is required to deliver a thin wide stream of stock including paper pulp fibers in suspension, across the width of the forming section. This stream is deposited on the drainage wire of the forming section, or Fourdrinier, the water suspending the fibers being drained away and the sheet of paper being thus formed on the wire.

This stream of stock may vary from one quarter of an inch or less to two inches or more in depth and may be as wide as 360" or more. The velocity of the stock stream may be less than fifty feet per minute or greater than four thousand feet per minute, these parameters depending on the size and speed of the forming section and the type and weight of the paper being made.

The stock stream may contain in suspension or solution paper pulp fibers, textile fibers, clays and other minute particles, fillers, etc., various chemicals and dyes which contribute to the various qualities desired to be obtained in the finished paper product.

It is important that the stream discharging from the headbox be of uniform velocity, and state of suspension and concentration, as well as uniform as to volume of liquid across its width, as any variations in these qualities will produce variations in the finished paper such as streaks, thin spots, etc.

The paper machine headbox has for its purpose taking the stream of stock flowing in a single pipe and converting it to a wide flat stream of relatively narrow depth and desired velocity; reducing turbulence in the stream, causing variations of delivery to an acceptable minimum, and maintaining and delivering the stock in a uniform state of dispersion of all solid elements to permit formation of a desired and uniform sheet of paper. These functions must be performed with stock containing a variety of solid materials without separation, build-up, or collection of dirt.

In the prior art, headboxes have generally provided only a relatively poor distribution system which is followed by a relatively large dead zone, to attempt to eliminate turbulence and large scale variations in flow from the distribution system. The stock in the dead zone in the absence of high flow velocities tends to flocculate and some elements may settle out of the dead zone. As a result of this, the stock is delivered to the discharge nozzle of the headbox in a non-uniform condition of dispersion which is not suitable to formation of a proper paper sheet. There is also a tendency for a non-uniform flow from the distribution passing through the dead zone undiminished, causing serious wave-like variations in flow of the final stream onto the forming wire.

To aid in evening off the flow of the stream and in mixing the stock more uniformly, one or more rotated distributor rolls or perforated holey rolls are often placed in the flow, but these have been found not to be a completely satisfactory solution of the problem, and they are expensive to manufacture and drive. i

In view of the above, it is the object of the present invention to provide a headbox capable of delivering a more uniform stream from the slice thereof under a wide range of conditions. The novel headbox is very simple and compact in design and construction and does not require rotating perforated or holey rolls.

It is well known in hydraulics that uniform flow of a stream may be achieved or approximated and large scale turbulence converted to small scale turbulence by introduction into the flowing stream of devices such as screens, so that as the stream flows through such a screen it produces a large pressure drop by flowing through small open ings or apertures comprising a small area of the total cross section of the stream. The use of such devices however in the paper industry has been impossible as the small openings are quickly plugged by the paper and other fibers forming a dam preventing operation of the machine.

It is an object of this invention to obtain improved distribution of stock flow, dispersion of stock and freedom of stock steam from unwanted turbulence by the use of such a screen, but in combination with means for hydraulically maintaining the screen clean and free of plugging Without however the use of any moving parts. The means for achieving this unique result consists in supplying stock to the upstream side of the screen through a number of nozzles which discharge against the upstream side of the screen and create a higher level of turbulence in the course of dissipation of the energy of the nozzles, this turbulence acting to scrub the upstream side of the screen clean of fibers or other solid materials tending to plug the relatively small openings in the screen, so that the screen accomplishes its intended function of providing continuously a uniform flow of the stock without plugging.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings in which:

FIG. 1 is a cross sectional view through a headbox according to the present invention showing a preferred embodiment of the invention;

FIG. 2 is a similar view in diagrammatic form showing the application of the principle of the invention to a different form of headbox;

FIG. 3 is a similar view diagrammatically disclosing an alternative form of the invention;

FIG. 4 is a similar view showing another modification;

FIG. 5 is a diagrammatic view illustrating a sump applied to a more or less basic form of the present invention to extract and dispose of material of such size as may be unable to pass through the screen, and

FIG. 6 illustrates the invention with an overflow manifold applied thereto.

Referring now to FIG. 1, it will be seen that there is herein provided a manifold or supply pipe 10. This is preferably tapered with an entrance at its larger end at one side of the machine and a small overflow at the other side of the machine. It is to be understood that the manifold extends across the width of the machine and connects at regular intervals with respect to the headbox by means of a series of conduits 12, 12 attached to nozzles 14, 14 on the manifold. These conduits are conveniently hoses and are usually arranged in the lower portion of the manifold as shown in FIG. 1 so that air entrained in the stock tends to separate and pass out through the overflow.

The hoses 12 are of small area so that velocities therein are relatively high, creating a large pressure drop with respect to manifold 10. This pressure drop plus the tapering of the manifold and the overflow equalizes the flow in the hoses.

The hoses are connected to enter a chamber 16 through nozzles 18 which are connected to the two relatively inclined walls 20 of the chamber. The nozzles in pairs are directed generally speaking at right angles to each other creating at the point of impact in chamber 16 a higher degree of turbulence than would otherwise be the case.

A screen 22 is provided forming a wall of chamber 16 and the entrance to the headbox chamber 24. This screen contains a number of small perforations closely spaced, the total area of the perforations being only a small percentage of the total area of the screen. The stock passes from chamber 16 into the headbox through the perforations of the screen. The high turbulence of the jets or nozzles 18, 18 impinging on the screen at the upstream side thereof, prevents the perforations therein from being plugged by paper fiber or other solid materials contained in the stock flowing through the screen. The small holes in the screen produce high velocity jets themselves but they create a high pressure drop resulting in an equal flow through the holes in the screen. In addition, the energy dissipated by the high pressure drop is very effective for producing a uniform suspension of all materials in the paper stock, deflocculating fiber accumulation and intimately mixing all the components.

The stock passes into the headbox in excellent condition for discharge to the forming zone and the headbox contains a short open flow channel bounded in the top area thereof by an air dome 26.

The headbox is provided with a bottom 28, back wall 30, top 32, and a front wall 34. The front wall has a bottom lip 36 and a top lip 38 adjustable by rotation about the axis of a hinge at 40, these lips forming the discharge stream 42 which is deposited on the forming wire traveling about breast roll 44. A clevis 46 attached to adjusting screws 48 may be utilized to regulate the size of the opening forming the discharge stream.

A sensing device 50 detects the liquid level in the headbox and acting through a conventional controller device 52 and valve 54 regulates the pressure of the air supplied to the air dome 26 by the pump 56 and discharges through orifice 58 thus holding an air-stock interface level constant. The air dome is thus valuable in re leasing air from the stock and in providing the cushion for the hydraulic pulsations of the stock.

A typical headbox employing the principles of this invention might use the following design parameters for a headbox with a slice discharge of 180". In requiring a total flow of 12,000 gallons per minute, the manifold supplying the hoses would have an average liquid velocity of twelve feet per second with overflow about ten percent of the stock entering and would have an inlet pipe diameter of 21" and overflow diameter of six inches. It would use approximately one inch diameter nozzles arranged as seventy pairs at intervals of 2.57 inches and these supply the stock from the manifold to the screen. The velocity of the stock from the nozzles would be thirty-five feet per second and the pressure drop from the manifold to the upstream side of the screen 8.25 pounds per square inch. The screen should have one-eighth inch diameter holes, five holes per square inch for a screen open area of 6.2%. The screen area would be ten inches high by wide. Screen jet velocity would be thirty-five feet per second and pressure drop across the screen would be 8.25 pounds per square inch. For stock velocity following screen 22 of two feet per second, the liquid depth below the air dome should be 10.6 inches.

FIG. 2 shows the application of the construction of FIG. 1 to a full running headbox, i.e., without the air dome. A perforated rotating roll is also shown as at 60 to aid in evening the flow of stock when the screen is located some distance from the jet discharge. A plurality of such rolls may be used, in which case the screen element is acting primarily as a distributor in a more conventional headbox.

FIG. 3 shows an alternative method of developing the necessary turbulence on the upstream side of the screen 62 and this involves a number of jets in a single row 64 directed parallel and across a corrugated panel 66 roughly parallel to the screen 62, the corrugations providing a number of localized eddies 68 producing uniform turbulence across the upstream face of the screen.

FIG. 4 illustrates another embodiment of the invention in which the nozzles in this case merely comprise slots 70, 70 formed by solid members 72, 72 on the upstream side of the screen 74, these slots producing jets acting to oppose each other as shown by the arrows in this figure.

FIG. 5 shows the basic headbox described as shown in FIG. 1 but with a sump 76 provided in the chamber upstream of the screen. This sump is removed from the area of maximum turbulence and any material of such size as may be unable to pass through the small perforations of the screen 78 will tend to settle into the sump. Such rejection material can be removed intermittently or continually by means of the valve 80.

Referring now to FIG. 6 there is shown an example of the invention more or less as shown in FIG. 1 but including an overflow manifold 82. By diverting some flow to the screen 84 through a number of pipes to an overflow manifold such as shown in FIG. 6, the upstream nozzle velocity may be maintained as high as desired or necessary to keep the upstream side of the screen clean even at reduced flow through the screen. This overflow manifold will not always be necessary but under some circumstances it will be found to be desirable.

What is claimed is:

1. A headbox construction for papermaking machine comprising a stock distribution chamber, a second chamber, a headbox chamber, the second chamber being associated with the headbox chamber, means forming a passage from the distribution chamber to the second chamber, and a screen at the headbox chamber and separating the second chamber from the headbox chamber, means forming an outlet at the end of the passage leading into the second chamber, said outlet directing the stock flow against said screen at a relatively high velocity and thereby creating turbulence in the stock at the surface of the screen in the second chamber, whereby said screen surface is maintained substantially clean and the screen in free stock-passing condition.

2. The headbox construction of claim 1 including a second passage for the stock from the distribution chamber into the second chamber, means forming an outlet for the second passage, so that there are at least two separate stock flow streams into the second chamber, and said means forming said outlets being positioned as to direct said two stock flow streams generally toward each other.

3. The headbox construction of claim 1 including a second passage for the stock from the distribution chamber into the second chamber and means forming an outlet for the second chamber end thereof, said means forming outlets being located on relatively inclined axes directed toward each other causing the two stock flow streams to infringe on each other.

4. The headbox construction of claim 1 wherein said second chamber includes a wall spaced from the screen, said wall including an indented portion facing the screen, the outlet for said passage being located to direct the stock flow against the wall as well as against the screen,

UNITED STATES PATENTS 3/ 1965 Calehutf 162-343 X 4/1967 Knowles 162-216 X S. LEON BASHORE, Primary Examiner 10 R. D. BAJEFSKY, Assistant Examiner U.S. Cl. X.R. 

